Composite structure



Patented Nov. 26, 1929 a U "r RICHARD PAUL CARLTON, OF ST. PAUL, MINNESOTA, ASSIGNOR TO MINNESOTA MINING AND MANUFACTURING COMPANY, OF ST. PAUL, MINNESOTA, A CORPORATION OF MIN1\TESOTA COMPOSITE STRUCTURE No Drawing. Application filed December '29, 1923, Serial No. 683,523. Renewed June 28, 1927.

This invention relates to abrasives and the like and more particularly to moistureproof flexible abrasive devices, and more especially with reference to improvements in 5 moisture-proof, that is, water, oil and other wet proof abrasive'material which is characterized by tenacity and, preferably,flexibility, and which is capable of use in the presence of dampness or wetness without immediate disintegration due thereto, and specifically to so-called cellulosic binders.

It will be understood by those-skilled in the art that cellulosic material disclosed as employed by me is intended to include such cellulosic material, treated or otherwise, which may be suitable for employment in this connection, such for example, as cellulose nitrate, cellulose acetate and cellulose xanthogenate.

This invention is characterized as employing cellulose as one of its principal ingredients, in combination, where necessary, as will hereinafter appear, with a modifying agent for increasing the adhesive properties or" the cellulose and as well enhancing the strength thereof without interfering with or reducing its flexibility where desired, and while a.

specific modifying agentor agents are mentioned as this description proceeds, and while the invention is described for use as a moisture proof binder for sandpaper other abrasive devices, fabric or otherwise, it will be understood that they are set forth as illustrations of the employment of a particular ingredient or ingredients or proportions of such ingredients for my present purposes, and that the field of utility of the binder and the abrasive device is of wide application;

This invention has as one of its principal objects the employment of cellulosic material, such as cellulose nitrate, cellulose acetate, et cetera, as the basis for an improved binder for securing pulverulent or comminuted abrasive material to a flexible back.

use of a backing which may or may not be 5 Waterproof or moisture-proof per se or of a backing which may or may not be first rendered moisture-proof before receiving the binder and the abrasive. I- contemplate the employment of my invention for one or more of the following purposes, viz: as an improved binder per -se, and as a binder on paper or cloth which has previously been rendered moisture-proof, such as by oil saturation, varnish, moisture-proof glue, or the like, or by the employment of theme.- terial of this invention as a moisture proofing material for a backing.

'My practice hereinafter described which has resulted in the production of a moistureproof, highly tenacious and flexible abrasive sheet, has been carried on with cellulose in various forms, and various solutions and modifications; With the object in mind of producing the product in large quantities at a reasonable cost, I have employed among other things, the various nitro-cellulose products, including socalled leather solutions and those commonly known as powder dopes, made by converting powder, of which latter there were large stocks remaining as surplus material after the recent great war. This power dope, so-called, when reduced, afi'ords a cellulose nitrate solution of low fiber con tent and as a bond for moisture-proof abrasive devices is capable of being rendered practicable ii modified as hereinafter pointed out; The cellulose materials are generally classified according to their content of fiber and it will readily be understood that the better cellulose solutions contain a greater quan tity of fiber and therefore a better body is im parted to the material. I do not reject the higher fiber content-cellulose solutions, but I have found that by my invention I am enabled to use the cheaper grades by combining therewith in suitable proportions a modifying agent which is in itself moisture-proof, fiexible and tenacious for imparting to the cheapor grade of cellulose suitable body, tenacity, I

and adhesive quality without detracting from the flexibility of the product "when set. I

I have found that where cellulose is employed as a binder when applied with a suitable abrasive, to celluloid, the adhesiveness of the binder is materially increased as well as the loo tenacity ifa modifying agent is employed, and this is particularly true of the lower grades of cellulose or its derivatives. For this reason, and others to appear, I have employed cellulose in combination'with a modifying agent such as resin, either natural resin or synthetic resin. This invention also has a principal object thereof the employment of cellulose or the like and a modifying agent as a binder for attaching comminuted abrasive material to a sheet of fabric or the like. Therefore, the principal objects and advantages of this invention reside in the provision of an improved moisture-proof binder including cellulosic material; the provision of an improved flexible moisture-proof binder including cellulosic material and a modify ing agent; theprovision of an improved binder, including cellulosic material,.for attaching grit to paper sheets or cloth or fabric; and the provision of an improved binder characterized by flexibility,'tenacity, and imperviousness to moisture which includes cellulosic material and a modifying agent, for

the purpose of increasing the tenacity of the binder without reducing the flexibility or durability thereof.

As I have hereinbefore mentioned, the 'cellulose product known as powder dope, due to its low fiber content, for the purposes of this invention, requires a modifying agent or filler, and I have discovered that either "certain natural or synthetic resins combined a with the cellulosic material and with a suitable solvent produces a binder which is moisture-proof and is possessed of a high degree -of' tenacity and will readily combine with paper, cloth or a' suitable base formed of the contemplated than a binder not containing such a modifying agent.

Certain cellulosic solutions produced from powder are in some cases very explosive and others are not of an explosive nature. They may be classified as cellulosemononitrate which contains a percentage of nitrogen to about 7 percent; cellulose dinitrate containing 11 to 12 percent nitrogen; and cellulose trinitrate containing from 14.to14.15 percent nitrogen. I find that all these classes are readily soluble-in suitable solvents and are suitable for the purpose of this invention, though some of them would preferably require conversion to bring the high nitrates into a lower nitrate, such asby boiling with you dilute nitric acid, thereby preventing explosion either in manufacture or use.

The above classification of the cellulosic solutions merely serves to indicate these products as they are produced in their crude state, the finished product now obtainable in the open market being a solution of these-solid cellulosic materials. The quantity of the solid which is taken'up by the solvent determines the fiber content of the cellulosic solution. A solution wherein the fiber content is those skilled in the art that, the higher the percentage of fiber content, the tougher the film and therefore the more the substance becomes desirable for use as a binder such as for sandpaper.

. The usual solvents for nitro cellulose are amyl acetate, amyl alcohol, butyl alcohol, acetone and ether alcohol mixtures. There are a large number of cellulose solutions now in the market and as solvents-thereof amyl acetate or-amyl alcohol in combination with ben- .zene' (benzol) or fusel oil may be employed, the'fusel oil and benzene (benzol serving as thinners. In these cellulose solutions the solvents mentioned above are preferred because the resultant fihns are clear as distinguished from the result obtained when solvent with hygroscopic tendencies such as acetone is em ployed, due to the tendency of such solvents to absorb water from the air. It is therefore obvious that to make a moisture-proof binder it is preferable that the cellulosic solution be treated by either amyl acetate, amyl alcohol or other non-hygrosco ic solvent so as to prevent any absorption 0 moisture as explained.

I have, in the course of my practice, em-

ployed nitro cellulose varnishes, a particular one, for example, having a fiber content of approximately 30 percent of the solution, gum camphor being preferably a constituent of this varnish because it acts to materially reduce the 'inflammability thereof or the tend- 1 is imparted to the film produced by adding castor oil in small percentages, usually below 10 percent.

ency of the solution to explode. Flexibility In addition to these materials, that is, gum

results are obtained. Any of the gums mentioned hereinbefore are readily soluble directly in the varnish since the amyl acetate used as a solvent for the cellulose nitrate is also a rapid solvent for the gum.

Under ordinary'conditions the addition of any of the above mentioned gums to the highhave employed gum poner fiber content cellulose varnish is not so absolutely necessary as the addition of such gums to the cheaper cellulosic materials, such as that known as powder dope, but at all times materially improves the appearance, body and tenacity of the binder without interfering with the flexibility desired where the binder iao vis-'--applied to a flexible sheet. The cheaper cellulose dopes commercially available are usually dissolved in low boiling point alcohols and, ive an insufficient body for supporting the a rasive material, but the gums added to the cellulosic material retain their adhesive nature after the cellulosic film has had surfacezcoagulation and thus improve the aggregateas a binder.

In the employment of cellulosic solutions wherein the fiber content is high, amyl acetate or amyl alcohol is employed by me as the solvent as this materialdries comparatively slowly which makes it possible for the comminuted abrasive to penetrate the film applied to the paper or fabric before the same hashad surface coagulation.

From the foregoing it will be seen that in the case of cheaper dopes itis necessary to modify the cellulos'ic solution in order to permit of application of the abrasive substance before the film of adhesive congeals, and that in the case of the more expensive dopes I utilize a solvent having desired predetermined qualities.

In manufacturing an abrasive sheet in .accordance with thisinvention, and assuming that the cheaper dopes are employed in the binder, it will be understood from the foregoing that any of the gums hereinbefore mentioned may be combined with the cellulosic solution for two purposes at least, the principal purpose being to increase the tenacity of the solution and the binder, and secondly to retard the drying sufficiently to permit of introduction of the abrasive material into the binder before coagulation or skinning over has set in. The addition of either the natural or synthetic resins will accomplish this result very nicely and one example of a practicable application of this invention as to proportions employed is as follows: J

10 parts 30 oz. cellulose nitrate solution, part gum pontianak added directly to above solution, A, part gun camphor, A; part castor oil.

In "the practice of my invention I find that success is obtained in the employment of a plasticizer, such as gum camphor; and I also find that for certain purposes the combination of an acetate, a ketone, such as acetone, benzol, and piasticiz'er and a gum such as gum pontianak combined with the cellulose nitrateIsolution gives desirable re sults. i

In order get a form which can be used so properties essential for o .tmn duction basis, such even .-fiowin spreading on the backing used, there be a certain balance of high, medium and low boiling solvents to obtain the proper rate of evaporation. To get the gum, like of nitro ceiluime n and posses-F;

damrnar, into solution, and the nitro-cellulose a filler, benzol, and a plasticizer.

such as butyl, and.

This in turn Benzol is used as a'diluent and also as a solvent for the gums used because of its comparatively low cost. It functions to reduce the viscosity'of the 'nitro-cellulose solution containing gums so that it is easier to manipulate in the abrasive coating process.

- Camphor, castor oil, phosphates, such, for example, as tri-cresol phosphates; tartrates, such as butyl tartrates, phtholates such as dibutyl phtholate have all been successfully employed by me and form excellent plasticizers or softeners. The function of such a p'lasticiZer or softener is to make the resulting film tough, elastic, flexible, adhesive and permanent.

The function of the gum is to give adhesion, body and hardness to the coating and to render the coating more impervious to moisture. This increase in the hardness of the film is a very desirable feature in producing agood abrasive paper because the abrasive grains on the paper undergo very severe service in the art of rubbing or grinding the materials on which they are being worked, and by increasing the hardness of the film the grains are more firmly held in place and stick on to the backing longer and more securely so that the life of the abrasivearticle is increased. The gum also increases the body of the coating material without increasing the viscosity thereof, and this is highly desirable- Being cheaper than nitro-cellulose, many gums tend to reduce the cost. In increasingthe hardness by the use brittleness, and to ofiset this and secure plasticity is one of the functions of the plasticizer, such as camphor.

I find that I am enabled to produce a sucthe- :ual bac ing incorporating thereon a film nitro-cellulose composition including a low boiling solvent, such as other alcohol mixtures acetate, for retarding the evaporation, a gum acting as an element for giving body to the composition, that is, in the nature of Therefore,

cessful waterproof abrasive product with med by evaporation from a modified ahigh boiling solvent, such as amyl and of a gum there is a tendency to 69 and properties as cellulose nitrates but-are to this end the waterproofing substance may be proxylyn dissolved in a proper solvent, such as an acetate, with or without other acetates such as ethyl alcohol, and with or without other alcohols, ketones like acetone,-

methyl ketones or camphor. v

I also contemplate applying the binder of acetone oils, benzol and this invention to a base layer or member which is formed 'of material of the same nature, such as applying the cellulose binder to a celluloid sheet or strip or disc (the arrangement in such a case preferably including first the celluloid sheet, secondly a coatin of my improved binder, then a coating of t esamebinder containing grit applied thereto, and

' lastly a sizing coating. In this manner the continuity'of the base layer is not disturbed ori inal strength. I also contemplate employing this invention in connection with oiled paper or with any other paperor fabric which has previously been rendered Waterproof or moisby the grit-and the base layer thus retains its ture-proof by impregnation or partial impregnation or by applyin a coating of water proof material to the back thereof. Such waterproofing material may hindersuitably thinned. i r

' After the product is set, I apply a sizing coat or coats which maybe of the samesolu tion as that'used for carrying the grit but be my present generally without thinning it, though, of

course, where a very heavy body solution such as those referred to hereinbefore is employed it is necessaryto thin such a solution to a suflicient extent to facilitate its handling and any of the solvents mentionedhereinbefore may be employed for this purpose.

Again, especially in employing-the cheaper dopes, such as cellulose solutions having a small fiber content, it is desirable that when applied topaper, the latter be sized to im-' prove the bond between the base and the adhesive, and to prevent the base or maklng coat from penetrating too greatly, so that this making coat of the binder will not be unduly. reduced in strength but will be thick enough to. receive the abrasive substance.

The application of a. sizing coat to the-base may be followed advantageously, even with the higher fiber content cellulose solutions.

There is a considerable quantity of cellulose dopes of other kinds manufactured and.

in the market today and produced similarly to cellulose nitrate, such for. example as cellulose acetate and cellulose xanthogenate. These cellulose dopes are usually non-inflammable and have much the same characteristics as a rule'more viscous and therefore more difficult to handle in manufacturing. I have carried on practice with such cellulose dopes, and while satisfactory rough results are obl tainable, in cases of these solutions and other solutions of low fiber content itv is desirable that repeated layers of the solutions be applied to produce a composite film so'as to attain the desired penetration, thickness and strength and tenacity, whether for the bind-' in" coat or for the sizing coats. J

,In theproduction of cellulose acetate dope,

cotton fiber, for example, may be subjected to the action of acetic anhydrid, and the resultant solid cellulose acetate dissolved in suitable solvents, such as nitrobenzol, chloroform, etc. In the production of cellulose xa'nthogemate, the cellulose may be 'subjected'to the action of caustic soda, and then dissolved in suitable solvents such as carbon bisulphide. The following formula is suggested for a cellulose acetate solution applicable as a bond for sandpaper:

10- parts saturated solution cellulose acetate in acetone, 1 part shellac gum, parts'cast'or oil. The following formula is suggested for the production of cellulose xanthogenate but is only a making process for this substance:

2 parts cotton fiber, 30 parts 15% caustic soda solution. Steep for '24 to' 36 hours.

Add 1 part carbon bisulphide.- Stir from time to time until dissolved. Thin to a working consistency with water or additionalcan bon bisulphide.

Having thus described my invention'and illustrated its use, what I claim as new and ,desire'to secure by Letters Patent is:

, 1. .A flexible abrasive device comprising a plurality of moistureproof layers of cellulosic material united to form a substantially.

.homogeneous piece, a flexible modifying agent for said layers for imparting increased strength and adhesiveness thereto, and abrasive material embedded in one of said layers; I

2. A flexible abrasive device for employment in awater-abrading operationcomprising' a plurality of moisture-proof layers intimately united to form a substantially homogeneous piece, a modifying agent embodied in one of said layers, a moisture-proof flexible base for'said layers which is continuous' and unbroken and abrasive material embedded in oneof said layers.

united to form a substantially homogeneouspiece, a modifying agent embodied in one of .said layers, the base layer being continuous and unbroken to impart strength to the device, and abrasive material embedded in one of said'layers.

5. A flexible abrasive device comprising a moisture-proof. layer, said layer having one of its surfaces provided with grit united I thereto by a cellulose cement containing a modifying agent.

6. A flexible abrasive device comprising a moisture-proof layer of flexible material containing a modifying agent, said layer having one of its surfaces provided with grit united thereto by a cellulose cement containing a modifying agent.

7. An abrasive device comprising a moisture-proof base layer provided with a coating of a material having a modifying agent therein, said coating having one of its surfaces provided with grit united thereto by a cellulose cement which is a partial solvent of the material of said coating.v

8. An abrasive device comprising a moisture-proof base layer provided with a coating of a material having a modifying agent therein, said coating having one of its sur faces provided with grit united thereto by a cellulose cement containing a modifying agent and which cement is a partial solvent of the material of the base layer.

9. An abrasive article comprising a moisture-proof flexible body layer of cellulosic material, having a modifying agent therein for increasing its tenacity, and having a gritcarrying coating of moisture-proof flexible T material intimately combined therewith, and

said coating having amodifying agent to form a substantially homogeneous moisture- -proof piece, the grit being carried by said coating. 7

r 10. An abrasive article comprising a moisture-proof flexible body layer having a mod-' ifying agent therein for increasing its tenacity and having a grit-carrying coating of moisture-proof flexible material having a modifying agent and intimately combined with the base layer to form a substantially homogeneous moisture-proof piece, the grit being carried by said coating, whereby the original strength of the body layer is not affected by the grit and the device is capable of continued use wet or dry until the grit is worn away.

11. The method of making abrasive sheets. which includes the step of applying thereto a binder containing cellulosic material and a modifying agent for the cellulose.

12. The method of making abrasivesheets, which includes the step of applying thereto a binder containing a material which is a partial solvent of the material of the sheet,

and increasing the bond between the adhesive and the sheet by the provision of a modifying agent in said binder.

13. The method of making a flexible abrasive article for use in a water abrading operation which includes applyin to a flexible sheet of fabric a grit or layer 0 abrasive particles, and a waterproof bond containing cel-" lulosic material of a nature to maintain the bonding effect throughout the effective abrading life of the abrasive article when em ployed in a water abrading operation, and applying thereto a plurality of auxiliary coats.

14:. The method of making a flexible abrasive article for use in a Water abrading operation which iiicludes applying to a flexible sheet of fabric a grit or layer of abrasive particles, and a waterproof bond containing cellulosic material of a nature to maintain the bonding effect throughout the effective abrading life of the abrasive article when employed in a water abrading operation, and applying thereto a waterproof auxiliary coat containing cellulosic material.

15. The method of making a flexible abrasive article for use in a water abrading operation which includes applying to a flexible sheet of fabric a grit or layer of abrasive particles, and a waterproof bond containing cellulosic material and a modifying agent of a nature to maintain the bonding effect throughout the effective abrading life of the abrasive article when employed in a water abrading operation, and applying an auxiliary coating to the article, said auxiliary coatingincluding a modifying agent for reinforcing the bond.

17. A new article of manufacture in the nature of sandpaper including a flexible sheet of fabric, a grit or layer of abrasive part-icles, and a waterproof stable adhesive binder including cellulosic material interposed between the grit and said sheet and of a nature to maintain the'bonding effect throughout the effective abrading life of the abrasive article when used in a ,Water abrading operation, and an auxiliary coat applied to said article containing cellulosic material and a modifying agent for strengthening the bond.

18. As a new article of manufacture, sandpaper, including a flexible sheet of fabric as a base, a waterproof stable grit retaining adhesive including cellulosic material and a modifying agent applied to said fabric and adapted to form a connection with the-base which is waterproof and stable when used in a water abrading operation but not detractin materially from the flexibility thereabrasive material carried by said binder.

of when dry, and a pulverulent abrasive material applied to said adhesive.

' 19. As a new article of manufacture, sand paper, including a flexible sheet of material as a base, a waterproof stable grit retaining adhesive containing cellulosic material'applied to said base and adapted to form a connection therewith which is waterproof and stable when used in a water abrading oper- 0 ation but not detracting materially from the flexibility thereof when dry, and a pulverulent abrasive material applied to said adhesive while still in a viscous state.

20. In a flexible and waterproof abrasive. article, a flexible base, a flexiblebinder which '30 which is flexible, stable, waterproof and highly resistant to deterioration when used in a.

water abrading operation, and a pnlverulent 22. An abrasive product comprising a flexible backing having abrasive grains attached thereto by a nitro-eellulose composition; con

taining aresin.

23. An abrasive product comprising a flexible backing having abrasive grains attached 40 thereto by a ntro-cellulose composition contalmng a resm and a plastlclzer.

24. An abrasive product comprising a.flexible backing having abrasive grains attached thereto by a nitro-cellulose comp0sition,,ineluding an acetate, an alcohol, a ketone, benzol, a plasticizer, and a'resin.

' 25. An abrasive product comprising a fiexible backing having abrasive grains attached thereto by a nitro-cellulose binder contain-- ing an acetate, an alcohol, a ketone, benzol, camphor, and a resin. v

26. An abr'asive product comprising a'flexible backing having abrasive'grains attached thereto by a nitro-cellulose composition con- 55 taining an acetate, an alcohol, a ketone, a benzol-type hydro-carbon, and aplasticizer.

27. An abrasive product comprising'a flexible backing having abrasive grains attached thereto by a nitro-cellulose composition containing a solvent, camphor, and aresin.

28. An abrasive product comprising a flex ible backing having abrasive grains attached thereto by a binding material containing nitro-cellulose, a resin, and a plasticizer.

29. An abrasive product comprising a flexible backing having abrasive grains attached thereto by a bmder consisting of 'nitro-cellulose composition, a resin, and a camphor.

30. An abrasive product comprising a flexible backing having abrasive grains secured thereto by a compos1t10n conta1ningnitrocellulose, a highboilingsolvent, a low boiling ,taining nitro-cellulose, a resin for giving body to nitro-cellulose, and a substance for p rendering the composition tough and permanent and for overcoming the brittleness of the resin. v

32. An abrasive product comprising a flexible backing having abrasive grains attached thereto by a flexible film containing nit'rocellulose, a resin for giving body to the nitro-- cellulose,fand'a plasticizjer for rendering the 'jfilm flexible, tough and permanent.

33; An abrasive product comprising a flexible backing having abrasive grains attached thereto by a film which is resistant to water,

such film being deposited from a slow evaporating nitro-cellulo se composition injsolution with a low boiling solvent, a high boiling solvent for retarding the evaporation thereof and by which an even spreading of the, fihn is secured, a resin for giving body to the composition, benzol, which forms a sol-' vent for the resin, and a plasticizer for im- "parting permanent toughness and flexibility 'to the film. v V l 34. As a new article of manufacture a sandpaper productcomprising a fabric base and abrasive material adhesively associated with said base by waterproof cellulosic coating. material, said coating material containing a filler andalso an emollient to maintain flexibility in the filler and the associated cellulosic material.

35. As a new article of manufacture a sandpaper product comprising a fabric base, abrasive material adhesively associated with said base, and a waterproofcoating of cellulosic f material, resin and oil, in which the cellu- ."losie material maintains the position of the abrasive grains on the base, the resin' serving as a filler and'the oil as an emolhent maintain flexibility.

36. As a new article of manufacture, a sand paper product comprising a fabric base and. abrasive material adhesively associated with.

one surface of said base by waterproof coat ing material, the other surface of said base being covered with a cellulosic coating material containing a filler and also an emollient. to maintain flexibility in the filler and the associated cellulosic material, said coating forth in claim 36 in which the abrasivematerial and the coating material by which it is adhesively associatedwith the base adhesively supports an added coatingof waterproof cellulqsic material containing a filler and also an emollient to maintain flexibility in the filler and the associatedcellulosic material forming a film in the nature of a matrix for' the abrasive particles through which the abrasive particles, as they wear away, gradually penetrate without disturbingthe matrix effect of said added film.

38. anew article of manufacture, a .sandaper product comprising a fabric base and a rasive material adhesively associated with one surface of'said base by Waterproof coating material, theother surface of said base being covered with a cellulosic coating -material containing a'filler and also an emollient consisting of an -.oil to maintain flexibility in the filler and the associated cellulosic material, said coating constituting a protective film to prevent frictional displacement of the. fibres constituting the fabric base in the use of the article. 7

39. An article of manufacture such as set forth in claim 38 in which the abrasive material and the coating material,- by which it is adhesively associatedwith' the base, adhesively supports an added coating of waterproof cellulosic material containing a filler and also an emollient consisting of an oil to maintain flexibility in the filler and the associated cellulosic material forming a film in the nature of a matrix for the abrasive particles through which the abrasive particles, as they wear away, graduall penetrate without disturbing the matrix e ect of-said added film.

40. As a new.article of manufacture, a

sand-paper product com rising a fabric base, abrasive material adhesively associated with the surface of said base by a matrix consisting of cellulosic material modified by the.

addition thereto of a resinous filler, an emollient consisting of an oil and an acetate and a plasticizer.

41. An article of manufacture such as set forth in claim 40, in which the. opposite sur- I face of the fabric base is treated with a waterproofing material to prevent the frictional displacement of fibres when thepaper is used wet; i I 42. As a new article of manufacture a sandpaper product comprising a fabric base, abrasive materialadhesivelyassociated with the $f.l1rface of said base by a matrix consisting of cellulosic materialmodified by the addi- ,tion thereto of a resinous filler and an emollient consisting of an oil and an acetate.

' In testimony whereof I have "hereunto .signedmy name.

4 RICHARD PAUL CARLTON. 

